1. Field of the Invention
The present invention relates generally to an apparatus for artificially lifting fluid from a well bore, and more particularly, but not by way of limitation, to an improved jet pump assembly for supplying gas into a well bore to remove fluid therefrom.
2. Brief Description of Related Art
Various types of techniques and apparatus have previously been employed to purge fluid from a well bore. The techniques and apparatus selected depend on the condition of the well, such as well pressure, well depth, volume of fluids produced, availability of energy, equipment cost, and other factors.
Typical of such techniques and apparatus that have been employed to remove fluid from the well bore are submersible pumps, sucker rod pumps, gas lifts, and jet pumps. Although each of these techniques and apparatus have been effective in removing fluid from the well bore, such prior art techniques and apparatus have certain negative aspects. For example, when employing submersible pumps and sucker rod pumps to remove fluid from a well bore, the installation cost of such equipment is extremely high, thereby making the use of such equipment cost ineffective for lifting relatively small volumes of fluid. Further, submersible pumps and sucker rod pumps require frequent and time consuming maintenance.
The apparatus and techniques of employing a gas lift to remove fluid from the well bore are generally less expensive than the use of a submersible pump or a sucker rod pump. A gas lift is a mechanical process in which gas is used as the lifting medium to remove the fluid from the well bore. Gas is injected down the annulus of the well bore to a gas lift valve disposed in the tubing. The gas enters the tubing through the gas lift valve and lifts the fluid accumulated above the gas lift valve to the surface.
Like submersible pumps and sucker rod pumps, gas lift systems are expensive to install thereby making the use of such equipment cost ineffective for lifting relatively small volumes of fluid. Further, while maintenance costs are generally less than those of submersible pumps and sucker rod pumps, gas lift systems, particularly the gas lift valves, require time consuming maintenance.
Hydraulic or downhole jet pumps have previously been employed to remove fluid from a well bore. Hydraulic or downhole jet pumps generally include a power fluid line operably coupled to the entrance of the jet pump and a return line coupled to receive fluids from a discharge end of the pump. The jet pump includes a venturi or an area of constricted flow. As the pressurized power fluid is forced through the venturi of the downhole jet pump, the power fluid draws in and intermixes with the production fluid. The power fluid and production fluid are then pumped to the surface through the return line where the production fluid and the power fluid are recovered. Jet pumps are often advantageous because they generally involve substantially fewer moving parts than mechanical pumps, thereby increasing the reliability of the jet pump. However, because the flow of the fluid through the jet pump is restricted, the volume of fluid that the jet pump is capable of moving to the surface is also restricted. Furthermore, the restricted flow path creates a high volume environment which may result in damage to tubulars, such as the casing. Finally, the restricted flow path is susceptible to becoming clogged by fines and scale, thus requiring the jet pump to be pulled from the well bore.
Thus, a need exists for an improved jet pump assembly to remove accumulated fluid from a well bore. However, such an improved assembly must also be cost efficient and substantially maintenance-free. It is to such an improved apparatus that the present invention is directed.